1. Field of the Invention
The present invention relates to a magnetic sensing element primarily used for a hard disk device, a magnetic sensor and the like and to a method for manufacturing the same. In particular, the present invention relates to a magnetic sensing element having excellent heat resistance and electrostatic-discharge-damage resistance and to a method for manufacturing the same.
2. Description of the Related Art
FIG. 15 is a partial sectional view of the structure of a conventional magnetic sensing element, viewed from the side of a surface facing a recording medium.
A multilayer film 5 composed of a first antiferromagnetic layer 1, a pinned magnetic layer 2, a non-magnetic material layer 3 and a free magnetic layer 4 is provided on a substrate, not shown in the drawing. A pair of ferromagnetic layers 6 and 6 and a pair of second antiferromagnetic layers 7 and 7, each having a spacing in the track-width direction, are laminated on the free magnetic layer 4. Electrodes 8 and 8 are provided on the second antiferromagnetic layers 7 and 7.
The magnetization of the pinned magnetic layer 2 is pinned in the Y direction shown in the drawing by an exchange coupling magnetic field generated between the first antiferromagnetic layer 1 and the pinned magnetic layer 2. On the other hand, the magnetization of the free magnetic layer 4 is aligned in the X direction shown in the drawing by exchange coupling magnetic fields generated between the second antiferromagnetic layers 7 and 7 and the ferromagnetic layers 6 and 6.
A system in which magnetization control of the free magnetic layer 4 is performed by the exchange coupling magnetic fields between the second antiferromagnetic layers 7 and 7 and the ferromagnetic layer 6 and 6, as shown in FIG. 15, is referred to as an exchange bias system.
The track-width dimension Tw of the magnetic sensing element shown in FIG. 15 is regulated by the spacing in the track-width direction (the X direction shown in the drawing) between the second antiferromagnetic layers 7 and 7.
The magnetization of both side regions C and C of the free magnetic layer 4 overlapping the second antiferromagnetic layers 7 and 7 is strongly pinned in the track-width direction (the X direction shown in the drawing) in order that the magnetization direction does not fluctuate even when an external magnetic field is applied. On the other hand, the magnetization of the central portion (sensitive region) D of the free magnetic layer, sandwiched between the second antiferromagnetic layers 7 and 7, is aligned in the track-width direction, following the magnetization of both the side regions C and C. However, adjustment is performed in order that the magnetization direction fluctuates when an external magnetic field is applied.
The magnetic sensing element of the exchange bias system can properly perform magnetization control of the free magnetic layer 4 even when the dimension of the track-width dimension Tw is reduced, and therefore, the magnetic sensing element is believed to become the mainstream of magnetic sensing element matching a future increase in packing density.
However, the magnetic sensing element shown in FIG. 15 has the following problems.
The ferromagnetic layers 6 and 6 are laminated on both the side regions C and C of the free magnetic layer 4 of the magnetic sensing element shown in FIG. 15. In both the side regions C and C, the total film thickness Tt of the free magnetic layer 4 and the ferromagnetic layers 6 and 6 is larger than the film thickness Tf of the central portion D simply composed of the free magnetic layer 4.
Consequently, static magnetic fields E generated from the ferromagnetic layers 6 and 6 and static magnetic fields generated from both the side regions C and C of the free magnetic layer 4 enter into the central portion D, and the magnetization of the central portion D, in particular the magnetization of regions adjacent to both the side regions C and C is pinned.
As a result, a dead zone in which magnetization is unlikely to fluctuate with respect to an external magnetic field is generated in the central portion D, and in addition, the ratio of this dead zone to the track-width dimension is increased with such a reduction in track that the track-width region of the free magnetic layer is reduced to 0.18 μm or less. Consequently, the playback sensitivity is lowered.
Regarding a magnetic sensing element shown in FIG. 16, in which second antiferromagnetic layers 7 and 7 are directly laminated on both side regions C and C of a free magnetic layer 4, a phenomenon, in which static magnetic fields generated from both the side regions C and C of the free magnetic layer 4 enter into the central portion D, and the magnetization of the central portion D is pinned, occurs as well. Therefore, a problem occurs in that a dead zone is generated in the central portion D.
In FIG. 8 of Japanese Unexamined Patent Application Publication No. 10-124823, a magnetoresistance effect element (magnetic sensing element) is described, in which the film thicknesses of outer portions of both end portions (both side regions) of a magnetized free layer (free magnetic layer) are made smaller than the film thickness of a magnetic field detecting portion (central portion). This structure is believed to be able to reduce static magnetic fields which are generated from the outer portions of both the end portions of the magnetized free layer and which enter into the magnetic field detecting portion.
In the magnetic sensing element described in FIG. 8 of Japanese Unexamined Patent Application Publication No. 10-124823, the outer portions of both the end portions of the magnetized free layer are cut by etching so as to become thin, and films made of, e.g. an antiferromagnetic material, for applying bias magnetic fields are laminated thereon, as is clear from the description in the paragraph (0067) in the specification.
However, even when the film made of an antiferromagnetic material is laminated on an etched surface of the magnetized free layer made of an antiferromagnetic material, sufficient exchange coupling magnetic field cannot be generated. That is, regarding the magnetoresistance effect element described in FIG. 8 of Japanese Unexamined Patent Application Publication No. 10-124823, a problem of side leading becomes significant, in which the outer portions of both the end portions other than the magnetic field detecting portion also detect the magnetic field.